The recognition of molecules by organisms is important for survival. Molecules sensed at internal synapses are critical in the organization of neural pathways, other molecules are sensed by developing systems and thereby guide morphogenesis, molecules of external origin are detected by olfactory system and guide a variety of complex behaviors ranging from feeding to reproduction. The olfactory receptor neurons have the unique ability to regenerate. This fact renders the olfactory system significant in understanding brain function in health and disease. In the latter case epilepsy, Alzheimer's disease and other neurological disorders result in impaired olfactory function. The principal investigator's long term goal is a broad understanding of olfactory stimulus detection at receptors, encoding in the olfactory bulb, and subsequent animal behavior in states of normal and abnormal development. The focus of the present proposal is on encoding olfactory stimulus chemical energy at the receptor and in higher levels of olfactory circuitry. The salamander is used as a model to test the hypothesis that odorants are encoded in brain circuits as distributed parallel-acting processes. These must include both specific and broad-band responsivity and redundancy to account for time-invariant function given the continuous turnover of receptor cells. To test this hypothesis the principal investigator proposes to use molecular, developmental, and physiological methods to probe single neurons and neurons acting as an ensemble in odor-guided behavior.